8: ectosymbiosis

Question 1

what are the 3 types of ectosymbiotic behavioural mutualisms?

Answer 1

ant plant
ant aphid
pollination

Question 2

what is the basic overview of the acacia P.ferruginea mutualism?

Answer 2

plant provides ant with shelter and food in return ant can defend plant from herbivore attack

Question 3

list 3 plant specialist adaptations to deal with ant plant mutualism

Answer 3

• energy rich beltian body
• modified thorn domatia
• extra floral nectaries

Question 4

what are energy rich beltian bodies?

Answer 4

yellow fatty deposits on leaves that ant take to raise larvae

Question 5

what are domatia?

Answer 5

swollen body around thorns that ants use for nesting

Question 6

ant-plant mutualism has evolved many times but in how many genera?

Answer 6

100

Question 7

explain the example of Chamaecrista nectaries

Answer 7

they exude sugar via holes direct to the phloem

produced on leaves and stems

Question 8

what did Baker-Meio et al 2012 do and discover about EFN?

Answer 8

• removed some EFN and kept some present
• measured proportion of successful fruits host plants produced
• when no nectaries less successful fruit
• tested with ants present or not
• when no external seed predators more fruits even if nectaries removed
• the ants chase off the predators

Question 9

what is the acacia drepanolobium domatia example ?

Answer 9

• protected from large herbivores by ants
• ants provided with refuges in form of domatia and carbohydrates from EFN
• loss of large herbivores changes ant community
• mutualistic basis of symbiosis maintained by presence of large herbivores and in absence plant downregulates nectar secretion and domatia production

Question 10

in Palmer et al 2008 study what did do/find and what were the 4 ant species studied and how do they vary?

Answer 10

exclude or keep large herbivores

• less herbivores less active nectaries and less swollen thorns
• loss of large herbivores can cause changes in ant community
• C.mimosae, C.siostedti, C.nigriceps, T.penzia
• vary in their defence of host trees and use of host tree rewards

Question 11

in Palmer et al 2008 study what species was found to be a good and poor defender when looking at proportion of trees occupied?

Answer 11

C.s poor- when no large herbivores increase in ants

C.m good defender- when no herbivore reduction in trees occupied by ants as rely on tree for rewards

Question 12

in Palmer et al 2008 study what are trees colonised by poor defender like?

Answer 12

higher mortality rate and low growth rate

Question 13

in Palmer et al 2008 study what does the facilitation of highly destructive tree-boring insects by C.s provide?

Answer 13

mechanism for negative impact of ant on tree growth and survival

Question 14

what did Huxley find about the relationship between ant plants Hydnophytum and Myrmecodia and ants? (3)

Answer 14

• plants produce specialized multi chambered tubers as refugia for ants
• swollen bottom part of stem full of interconnected chambers with lots of air flow and nesting area
• ants defend host and defecate in tubers which provides host with mineral nutrients (important for epiphyte as nutrients hard to find)

Question 15

what did Huxley 1978 find when looking at the provision of mineral nutrients to the ant plant by ant faeces deposition inside tubers?

Answer 15

• made plants radioactive and measured this radioactivity in ants
• ant radiation detectable in plant and into shoots (suggesting plants are using the nutrients)
• ants spent the longest time in warted surface cavities full of microdebris
• the ants defecate more here (live elsewhere) as the warted surface has a higher SA so the plant can take up more nutrients

Question 16

what is honeydew and why is it produced by aphids and what do ants do?

Answer 16

waste sugar produced as aphids need huge amounts of sugar for a small amount of nutrients

• attract bacteria and fungi which isn’t good
• ants farm the aphids by feeding on the honeydew and defending the aphids from predators

Question 17

give 4 benefits of ant-aphid mutualism

Answer 17

• excess honeydew removed by ants, preventing fungal colonisation of sugar middens that could be fatal for the aphid
• ants defend immobile aphids from insect attack
• ants gain spatially and temporally stable carbohydrate and water source - ants protected aphid colonies more stable and persist longer

Question 18

give 7 costs to ant plant mutualism

Answer 18

• presence of mutualistic ants can strongly affect persistence of aphid colonies or founding new colonies by dispersal
• ants can limit aphid dispersal
• ant adaptations limit winged aphid dispersal and benefit ants by allowing unusually crowded aphid aggregations so more honeydew produced
• winged dispersal isn’t the only way aphids colonise new plants
• when crowded condition late instar aphids will leave colonies to wander to new locations on the same plant or ground to new host
• presence of ants can produce tranquilising effects on aphids

Question 19

in what 2 ways can ants limit aphid dispersal?

Answer 19

1. direct physical manipulation (ants may bite or remove wings from aphids)
2. chemical influence (mandibular secretions of ants can inhibit wing development)

Question 20

give 3 points about how the presence of ants can have tranquilising effects on aphids

Answer 20

• limit motor functions
• attributable to direct contact with ants
• underpinned interspecific semiochemical communication

Question 21

what did Oliver at al 2007 discover about the walking speed of aphids in the presence/absence of ants ?

Answer 21

reduction in walking speed at high aphid density when incontact with ants due to ant semiochemicals

• took a long time to reach the edge of the petri dish when exposed to ants
• ants almost in control of the symbiosis

Question 22

what is pollination?

Answer 22

the transfer of pollen from anther to stigma of a carpel for the purpose of fertilising ovules

Question 23

according to Bronstein et al 2006 what does preserved gymnosperm pollen in insect guts provide evidence for?

Answer 23

that insects were consuming pollen as far back as permian, before the angiosperm evolution in the late jurassic

Question 24

according to Bronstein et al 2006 why did excess pollen likely evolve and when did nectar likely evolve and how can this be inferred?

Answer 24

excess pollen- first reward for early insect mutualists by late palaeozoic
nectar- before late jurassic, inferred from evolution of specialised nectar sucking mouthparts in diptera

Question 25

what were early angiosperms and insects likely to be like?

Answer 25

generalised pollinators

insects lacked adaptations for flower feeding

Question 26

what is an example of an honest signal used by flowers as a signal of quality?

Answer 26

fluctuating asymmetry

Question 27

what is fluctuating asymmetry and what is it a measure of?

Answer 27

small random deviations from bilateral/radial symmetry
measure of phenotypic quality of individuals indicating ability of controlled development under given environmental and genetic conditions

Question 28

what do nocturnal insects use to find the host?

Answer 28

perfumes or other odor based signals

Question 29

what did Moller 1995 discover and measure when studying floral asymmetry?

Answer 29

tested if floral symmetry reliability reflects phenotypic quality measured in terms of pollinator rewards and if pollinators respond to the symmetry

• lower nectar with increasing asymmetry
• symmetrical flowers produce more nectar/reward
• strong relationship between degree of symmetry and number of visitations

Question 30

what is an example of a deceptive signal and a plant that does this?

Answer 30

highly symmetrical but not producing much nectar

• bee orchid
• produces no nectar
• lures male bees by producing scents mimicking insect sex pheromones and acting as male morphological mimic

Question 31

what did Oliver at al 2007 discover about how ants often limit aphid dispersal?

Answer 31

by removing wings and chemical manipulation of wing development pathway

Question 32

what did Oliver at al 2007 discover for how the ant manipulation of aphid walking speed and dispersal can be detrimental or beneficial?

Answer 32

detrimental to aphid: if aphid dispersal used to reduce competition

beneficial: if dispersal used as enemy escape